• Posterior belly arises from mastroid process. innervate by CN VII (facial)
• Anterior belly arises from mandible. innervate by CN V3 (trigem)
• the two bellies connected by central tendon attached at hyoid bone.

Fx: rise hyoid bone, open mouth

attached at styloid process, bifurcate around posterior belly digastric and inserts on the hyoid bone.

Innervate by CN VII (facial)

• sternothyroid m
• sternohyoid m
• thyrohyoid m
• omohyoid m

locate within the pretracheal fascia inferior to hyoid bone. fx to depress the hyoid bone and larynx during swallowing and speaking.

• subclavian + common carotid arteries provide blood supplies to the head and neck. 
• External + anterior jugular veins are venous return for neck. Internal jugular provides venous return for head.
  

• Verterbral artery:  arises from the first part subclavian and ascends between anterior scalene and longus coli msucle, through transverse foramina of C6-C1, turns medially into foramen mangum to brain.
• Thyrocervical trunk: arises from the first part of subclavian. branches of thyrocervical include : suprascapular, transverse cervical, and inferior thyroid arteries.
  

branches from brachiocephalic artery, ascends within carotid sheaths along with internal jugular vein and vagus nerve.

• Internal carotid artery: gives off branches in the neck, and provide supply to the anterior, middle regions of brain, orbit and the scalp.
• External carotid artery: supply neck and face via: superior thyroid artery, lingual artery (supply tongue), facial artery, ascending pharyngeal artery (pharynx, palatine tosil), occipital artery, posterior aruicular artery (scalp post to ear), maxillary artery, superficial temporal artery (temporal region).
  

external jugular vein is forward at the angle of the mandible via joining of posterior auricular (drain scalp post to ear) and retromandibular vein (a. retro vein oin facial vein= common facial vein. Post d retro vein contributes to external jugular vein).

• arrive from ventral rami of C1-C4.
• cutanoeus (sensory) branches: pierce prevertebral fascia at the central regiong of the posterior border of the sternocelidomastoi muscle serving various region of the skin of the neck. the cutaneous branches of the cervical plexus are as follows:

1. lesser occipital nerve (C2)-skin over lower, lateral region of the scalp.
2. Greater auricular nerve (C2-C3)-innervates the skin over the parotid gland and angle of the jaw (this is only area of the face NOT supplied by CN V)
3. Transverse cervical nerce (C2-C3) innervates the skin over the anterior part of the neck.
4. Supraclavicular nerve (C3-4) innervates the skin over the lower portion of the neck, upper part of the chest, and the shoulder.

• Deep branch innervate muscle.
• C1 travel with CN XII innervates thyrohyoid + geniohyoid
• C1 form the superior root of the ansa cervicalis.
• C2-C3 join to form the inferior root of the ansa cervicalis which lies anterior to internal jugular vein.
• Most of the motor nerves from the cervical plexus branch from the ansa cervicalis supplies the infrahyoid muscle ( sternohyoid, sternothyroid, omohyoid)
• Phrenic nerve (C3-5) course vertically along the anterior scalene muscle between the subclavian artery and subclavian vein to inntervate the diaphrame.
  

• Trigeminal nerve (CN V): thru submandibulat triangle to innervate the Mylohyoid and anterior digastric muscle.
• Facial Nerve (CN VII) exists the skull, via the stylomastoid foramen, and provides brachial motor innervation to muscles of facial expression including the platysma muscle.
  
• Glossopharyngeal nerve (CN IX) exists the skull with CN X and XI, via jugular foramen, provide sensory innvervation of carotid sinus (baroreceptor) and carotid body (chemoreceptor)
• Vagus nerve (CN X) exist the skull with CN IX and CN XI , via jugular foramen, branche off into superior and recurrent laryngeal nerves. CN innervate pharynx larynx and gut tube.
• Spinal Accessory Nerve (CN XI) CN CI exist the jugumar foramen with CN IX and CN X, providing motor innervation to sternocleidomastoid and trapezius muscle.
• Hypoglossal nerve (CN XII) CN CII exits the skill via the hypoglossal canal and courses into the submandibular traignle, providing somatic motor innervation to the tongue muscle.
  

• the sympathetic trunk (chain) asceds from the thorax into the cervical region, within the prevertebral fascia along the longus coli and longus capitis muscles.
• The sympathetic trunk in the cervical region reveives only gray rami communicantes (no white rami). The sympathetic truk innervates the sweat and sebaceous glands, blood vessels, and the errector pili, dilator pupillae, and superior tarsal muscles.

• Boundaries: anteriorly (sternocleidomastoid m). Posteriorly (trapezius m). Inferiorly (the clavical).
• Roof of the posterior triangle:

1. Lesser occipital nerve
2. great auricular nerve
3. transverse cervial nerve
4. Supraclavicular nerve

• Floor of the Posterior triangle: formed by the prevertebral fascia. superficially to it are:

1. Inferior belly of the omohyoid m.
2. transverse servical artery: branch of thyrocervical trunk.
3. suprascapular artery
4. spinal accessory nerve [cranial nerve (CN) XI]

Deep to prevertebral fascia is:

1. Cervical muscle: splenius capitis, levator scapulae, posterior scalene, middle scalene.
2. Branchial plexus and subclavian artery.

• Boundary: anteriorly (midline down the neck). posteriorly (the sternocleidomastoid muscle). superiorly (lower border of the mandible)
• Submandibular triangle: bound by mandible, digastric, stylohyoid, mylohyoid muscles. contain submandibular salivary gland(innervated by parasympathetic fiber from CN VII), hypoglossal nerve (innervate the tongue)
• Carotid Triangle: formed by s. belly of omohod, p belly of digastric, sternocleidomastoid muscles.contains: Internal carotid, carotid sinus, cartid body, external carotid, superior thyroid a, lingual a, facial a, occipital a, ascending pharyngeal a, internal jugular v, tributaries of the invernal jugular v, CN IX, CN XII, ansa cerviclis, CN X.
  

• endocrine layer (the thyroid and parathyroid gland), a respiratory layer (the trachea and larynx), and an alimentary layer (the pharynx and esophagus).

• funnel-shaped, fibromuscular tube, extend from base of skull to cricoid cartilage, serve as common pathway for air and food.
• Nasopharynx: innervated by CN V-2
• Oropharynx:btw soft palate and epiglottis. Platoglossal arches=boundary between oral cavity and oropharynx. innervate by CN IX.
  
• Laryngopharynx:innervate by CN X
  

Pharyngeal constrictors:

• constrictor muscle attached posteriorly to the median pharyngeal raphe. composed of three overlapping muscles/

1. Superior pharyngeal constrictor
2. middle pharyngeal constrictor: stylopharyngeus muscle, CN IX, and the stylohyoid ligament course bteween the superior and the middle pharyngeal constrictor
3. inferior pharyngeal constrictor
   

1. stylopharyngeus muscle: attaches to styloid process of the tmporal bone, and the pharyngeal wall, between the superior and middle pharyngeal constrictors.
2. palatopharyngeus muscle: attaches to the soft and hard palates, and the pharyngeal wall.
   
3. salpingopharyngeus muscle: attaches to the auditory tube and the pharyngeal wall.

Stages in Swallowing!\

tensor=V

pala=X

gloss=XII

1. Tongues push bolus  back toward the oropharynx
2. palatoglossus and palatopharyngeus m (CN X) contract and squeeze bolus backward into oropharynx. Tensor veli palatini (CN V) and levator veli palatini (CN X) elevate and tense the soft palate to close the entrance into nasopharynx.
3. palatopharyngeus, stylopharyngeus, and salpingopharyngeus m elevate te hyoid bone and the larynx to close the opening to the larynx, prevent food from entering respiratory pathway.
4. sequential contaction of superior, middle, and inferior pharyngeal constrictor musces moves the food through oropharynx and the laryngopharynx into the esophagus, where t is propelled via peristalsis.

• Pharyngeal artery: branch of maxillary a. supply nasopharynx
  
• Facial artery: 
• ascending pharyngeal artery
• Pharyngeal plexus of nerves: CN IX (oropharynx) and CN X (laryngopharynx) and a small contribution from CN V2 (nasopharynx)

CN X originates in the brainstem and exits the jugular foramen to the posterior region of the middle pharyngeal constrictor muscle. neurons originating from the nucleus ambiguous in CN X supply all pharyngeal muscle except the stylopharyngeus. CN IX originates in teh brain stems to stylopharyngeus muscle.   

Gag reflect: sensory of gag reflext s suppied by CN IX and CN X. sensory limb of gag reflex is supply by CN IX. motor limb is supplied by CN X, lead to contraction of pharyngeal muscles.

Innvervation of the Scalp

• Posterior region: C2-lesser occipital, C3-greater occipital (cervical plexus)
  
• Anterior region:Supraorbital, Supratrochlear nerver (CN V1)
  
• Lateral region:Zygomaticotemporal-CN V2, auriculotemporarl nerve CN V3.
  

Vascular supply of the scalp

• External carotid artery: occipital, posterior auricular, and superficial temporal arteries
• Internal carotid artery: supraorbital and suprotrochlear arteries.

• Frontal bone: the unpaired frontal bone underlies the forehead .
• Parietal bone: paired parietal bones form the superal and lateral aspects of the skull.
• Temporarl bone: consist of squamous part form lateral portion, petrous part enclosed inner ear (cochlea, semicircular), middle ear (mallus, incus, stapes), and mastoid part (mastoid air cells), tympanic part (external auditory meatus, tympanic cavity).
• Occipital bone:framen magnum, transmits spinal cord and vetebral artery.

• coronal suture: join frontal and 2 pariental bones
• sagittal suture: joins paired parietal bones.
  
• squamous suture: joins the parietal and temporal bones
  
• lambdoid suture: joins the parietal bones with the occipital bones
• pterion: junction of frontal, prietal, temporal bones in the lateral aspect of the skull.

• Optic Canal: CN II
  
• Superior orbital fissure: CN III, CN IV, CN V1, CN VI
  
• foramen rotundum: CN V2
  
• foramen ovale: CN V3
  
• foramen spinosum: middle meningeal artery
• foramen lacerum:internal carotid artery travels over the roff of the foramen lacerum. the greater petrosal nerve courses through the foramen lacerum.

• Internal acoustic meatus: CN VII, CN VIII
  
•  Jugular foramen: CN IX, CN X, CN XI
  
• hypoglossal canal: CN XII
  
• foramen magnum:Medulla oblongata
  
• mastoid foramen: occipital artery, dura mater, mastoid emissary vein, mastoid foramen.

• Petrotympanic fissure: post. to mandibular fossa, opening of chordae tympani v, branch of CN VII, entering infratemporal fossa.
• Stylomastoid foramen:an oepning btw the styloid and mastoid processes of temporal bone. CN VII exists the foramen to innvervate muscles of expression
• Incisive canal:locate anteriorly, nasopalatine nv tranverse through the canal.
• greater and lesser palatine canals: locate posteriorly on hard plate. the greater and lesser palatine nerves tranverse the canals.

• CNN V, VII, IX, and X: innvervates most of head and neck
• CNN III, IV, and VI: orbit
• CNN I, II, and VIII: sensory for smell, sight, and hearing
• CN XII: tongues muscles
• CNN III, VII, IX, and X: cranial nerves that carry parasympathetic neurons.

• injurry--> loss of sensation in the skin of forehead and scalp. CN V-1 inervates cornea, therefore, mediation of the sensory limb of the corneal reflex is via the nasociliary branch.

• pass through foramen rotundum into the pterygopalatine fossa. This nerve provides general sensory innervation to the maxillary face. general sensory to maxillary face (between corner of the eyes and the corner of the mouths), palate nasal cavitu, paranasal sinuses and maxillary teeth.
• Injury--> loss of sensation in the skin over the maxilla and maxillary teeth.

• thru foramen ovale into the infratemporal fossa . CN V3 provides general sensory innervation to lower part of the face (lateral corners of mouth and bellow), include, anterior 2/3 of the tongue, the amndibular teeth, the mandibular face, and even part of scalp. CN V3 is a brachial motor neurons, innervate muscle of mastication (temporalis, masseter, medial and lateral pterygoid muscle), mylohyoid, anterior belly of digastric, tensor tympani and tensor veli palatine muscles.

• Brachial motor neurons: derived from second brachial arch. supply muscles of facial expression, as well as tapedius, psoterior belly of the digastricus, and stylohyoid muscle.
• Visceral motor neurons: provide parasympathetic innervation to almost all galnds of the head (lacrima gland, submandibular glandm sublingual gland, nasal, and palatal). only exception is parotid gland (innervate by IX).
• Special sensory neuron (Taste sensation from anterior 2/3 of tongue)
• General sensory neurons: transmit general sensation from a portion of the external acoustic meatus and auricle.

Brachial motor nerve trunk:

• Temporal
• Zygomatic
• Buccal
• Mandibular
• Cervical

Nervus intermedius

1. Greater petrosal nerve: preganglionic parasympathetic neurons that synapse in the pterygopalatine ganglion en route to the lacrimal, nasal, palatine glands.
2. Chorda tympani:exist the skull through petrotympanic fissure and join the lingual nerve from CN V3 in the infratemporal fossa.Chorda tympani has parasypathetic neurons that synapse in the submandibular ganglion en toute to innervate the submandibular and the sublingual salivary gland. chorda tympani also contains SA taste from the anterior 2/3 of tongue.
3. Auricular branches: arises from the external acoustic meatus and auricle

Damage: Bell's palsy

• tranverse the internal acoustic meatus with CN VII
• damage olead to ipsilateral deafness, tinnitus or ringing in the ear.

• general sensory: posterior third of tongue, oropharynx tympanic membrane, middle ear, and auditory tube
• Special sesnory: taste from posterior 1/3 of tongue
• visceral sensory: carotid sinus (baroreceptor) and carotid body (chemoreceptor)
• Brachial motor: stylopharyngeus m
• visceral motor: parotid gland.

Jugular foramen

• general sensory: skin of the posterior ear and external acoustic meatus
• visceral sensory: aortuc abd caritud bodies (chemoreceptors) and aortic arch (baroreceptor)
• Brachial motor: all palatal muscles (exceot tensor tympani); all pharyngeal muscles (exept stylopharyngeus m), and all laryngeal mm.
• Visceral M: heart, smooth muscle, and glands of the respiratory tract, gastrointestinal tube, and viscera of the foregut.

Jugular foramen

• Brachial motor: trapezius and sternocleidomastoid mm.

Jugular foramen

Somatic motor: tongue mm (except palatoglossus m)

Hypoglossal canal

provide somatic motor innervation to all intrinsic and extrinsiv tongue muscle

Injury to CN: when ask to stick out tongue, if there is a lesion on CN XII, the tongue will protrude toward the affected side.

dividied into vestibule, the semicircular canals, and the cochlea

• Vestibule: vestibule is the central portion of the bony labyrinth.
• vestibule window: the vestibular window serves as a mebranous interface bteween the stapes from the middle ear and the vestibule of the inner ear.
• Utricle and saccule: the membranous labyrinth within the vestibule consists of two connected sacs called the utricle and saccule. Both the utricle and saccule contain receptros that are sensitive to gravity and linear movements of the head.
  
• semicircular canals: the three bony semicircular canals of the inner ear are at right angles to each other. the narrow semicircular ducts of the membranous labyrinth are located within the semicircular canals. Recpetors within the semicricular ducts are sensitive to angular acceleration and deceleration of the head, as occurs in rotational movement.

• The cochlea is a coilde dtube divided into three chambers.
• scala vestibuli: forms the upper chamber of the cochea. begins at vestibular windown, continuous with the vestibule, contains perilymph.
• Scala tympani: forms the lower chamber of the trochlea. the scala tympani terminates at the cochlear window and contains perilymph.

• Cochlear duct: form the middle chamber of the cochlea. the roff of the cochlear duct is called the cestibular membrane, and the floor is called the basilar membrane. the cochlear duct is filled with endolymph and ends at the helicotrema. The cochlear duct house the spiral organ, where sound receptors transduce mechanical vibration into nerve impulse.

• CN VII and CN VIII enter internal auditory meatus.
• CN VII exits stylomastoid foramen (and petrotympanicc fissure as chorda tympani). chorda tympani innvercate the submandibular and sublingual salivary glands, and surveys taste sensation from the anterior 2/3 of the tongue.

• gravity and acceleration
• semicircular canals-rotation. 
• Semicircular canal function: ampullae-hair cels with gelatinous capua sense motion of endolymph around it.
• maculae-similar to ampullae, but boarder sheet, capula include statoconia to form otolith. These are "earstone"-crystal sitting on top of fluid, to give sensation of movement. 
• when your head is tilted back, otolith slides "downhill" distoring hair cells and give us the feeling of acceleration.

• Stapes at oval window convey pulses of sound from invus to vestibular duct.